Assessment of Long Term Impacts of Cadmium and Lead Load to Agricultural Soils in the Upper Elbe and Oder River Basins

Prieler S & Anderberg S(1996).Assessment of Long Term Impacts of Cadmium and Lead Load to Agricultural Soils in the Upper Elbe and Oder River Basins.
IIASA Working Paper.
IIASA, Laxenburg, Austria: WP-96-143

Abstract

This report investigates effects of long term load of two heavy metals, cadmium and lead to agricultural soils for a project area in Central Europe. The time frame for the historic analysis is 1955 to 1994. The major source of lead is atmospheric deposition. In the case of cadmium, besides atmospheric deposition, agricultural activities, such as P-fertilizer and manuring, are additional sources of heavy metal input to agricultural soils. Extremely high depositions that were measured in a "hot spot" region in the project area are included in the analysis. A soil model is used to perform a quantitative analysis of potential accumulation or release of cumulative heavy metal loads. A GIS database enables us to undertake a regional analysis. Potential future risks are addressed in a scenario approach covering the time frame 1995 to 2050.

For the majority of the project area there was no significant increase in cadmium and particularly lead soil concentration compared to background values and guidelines. The parts of the project area which had the highest cumulative cadmium deposition historic cadmium accumulation may be of concern. However these assessments related to long term suitability for agricultural food production depend on environmental criteria and the time frames taken into account. Locally, in hot spot areas, atmospheric deposition were and still are much higher and soil guideline values may be exceeded within 10 to 50 years.

The cadmium mass balance for the project area covering the period 1955 to 1994 suggests that from the cumulative load of 3062t of cadmium (about two thirds from atmospheric deposition and one third from agricultural sources), one third is lost (836t) and two thirds are accumulated in the soil (2226t).

Estimates of future atmospheric cadmium and lead deposition are low compared to historic depositions. Cumulative cadmium deposition during 1991 and 2010 is only 10 to 40% of the cumulative deposition during 1970 and 1990. The average lead deposition in 2010 is only 10% of the average deposition in the 70s or 80s.

Due to declining pH-value, triggered by the abandonment of agricultural land and/or a conversion into forest in scenario 1, major releases of cadmium are expected. Even the maximum assumed deposition is not high enough to compensate cadmium loss due to declining pH-value. The extent of decrease depends mainly on the assumed initial concentration in 1994 because cumulative future atmospheric deposition is very low compared to the cadmium already stored in the soils at present.

Scenario 2 assumes intensive agricultural production until 2050. Agricultural activities are now the major source of cadmium load to the soils. In most cases a study state will be reached, the maximum delta increase over the future 55 years is 0.08mg/kg.

In both scenarios lead soil concentrations are likely to decrease slightly in the future due to losses via erosion, which exceed atmospheric deposition.